Infrared Methods in Noninvasive Inspection of Artwork

The problem of attribution and forgery in artwork is quickly becoming more acute with the advance of both the technology and experience of painting forgers. Sometimes even an experienced expert is not able to detect counterfeits that have been made with almost the same materials and technique as the original. Further, even the substitution of the signature of a famous artist on a painting can dramatically increase its value. Another problem of interest is the examination process of a painting preceding its restoration. This procedure can show the restorer the most affected regions of a canvas and/or its delimitations, separating particular regions by the extent of their damage. For these reasons, the role of professional scientific examination is of great importance. Thus, scientific procedures based on modern high-technological devices and methods must be developed to enable both restoration pre-examination and complex forgery-detection. In this article the three infrared methods suitable for the inspection of art inspection are discussed. These include near infrared vision, thermography, and pulse phase thermography, a method never before used in art field. Through the use of several original masterpieces, these techniques are shown to be effective instruments for art inspection and restoration alike. They permit the detection of hidden underdrawings that were done before the painting was finished, concealed and altered signatures, and restored regions of pictures. These methods may also be used to locate delaminations between the paint layers and areas of varying paint thickness. INTRODUCTION Preserving the cultural heritage is an important problem for both art specialists and scientists alike. As the age of a masterpiece increases, it requires increasingly meticulous handling. For this reason it is necessary that the restoration process be extremely gentle – unprofessional treatment can have irreversibly adverse consequences. To treat a painting, a restorer needs complete information regarding its condition: degraded regions, type of pigments used, and the strength of the support and ground layers. Another concern is the possibility of both unintentional and intentional alterations, particularly forgeries. During the restoration process some parts of painting can be painted or even added. Related cases included altering or forging original signatures. Naturally, the addition of a famous painter’s signature onto any painting increases its price several times and is a common example of art fraud. Information regarding both these alterations and the condition of the paint can be extracted by using special scientific techniques. Among different imaging techniques, the first ones are obviously optical techniques, including 2D and 3D optical methods are widely used for imaging color acquisition, optical fluorescence imaging, etc. In addition to well developed optical methods, there are also such technologies as neutron illumination, X-ray scalpel beams, sonic tomography, vibro-acoustics, laser ultrasound, ultrasonic air-coupled 1 9th International Conference on NDT of Art, Jerusalem Israel, 25-30 May 2008 For more papers of this publication click: www.ndt.net/search/docs.php3?MainSource=65